Water Recirculation System

ABSTRACT

A water recirculation system for a shower unit comprises a plurality of reservoirs and switching means for selecting from which of the reservoirs the shower unit receives water. A pump recirculates water from a waste trap of the shower unit to the active reservoir. Each reservoir contains a heater. At the user&#39;s command, a system of valves is reconfigured so that the shower unit becomes supplied with fresh water circulated from a second reservoir. Meanwhile, the first reservoir is emptied, refilled and reheated to be ready for further use if required. Further pipes may be provided to allow preheating and circulation of the water in the system prior to use of the shower unit; and to allow the system to be flushed with water from a mains supply.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation of PCT/GB2012/050933, filed Apr. 27, 2012, which claims priority to Great Britain Application No. 1107310.3, filed May 3, 2011 and Great Britain Application No. 1202163.0, filed Feb. 8, 2012, the entire teachings and disclosure of which are incorporated herein by reference thereto.

FIELD OF THE INVENTION

The present invention relates to a water recirculation system, and in particular to a water recirculation system that may be employed in a washing unit such as a shower or a bath in order to recycle and save water.

BACKGROUND TO THE INVENTION

One of the biggest problems facing the population today, and increasingly more so over the next few decades, is the dwindling resource of water on this planet. Human beings simply cannot function without a water supply. We need a constant supply to consume just to stay alive, remain hydrated and regulate our bodies' temperature. In addition, everyday water is used in a variety of scenarios from simple domestic cleaning and washing purposes, to larger scale industry, cooling, cleaning, crop watering and leisure applications. Sooner rather than later the finite supply in aquifers will run out and the supply of fresh water circulating on Earth will cease to meet our needs, with some experts predicting that natural water stocks will run out quicker than those of supposedly more valuable fossil fuels such as oil and natural gas. Efforts are being made to reduce consumption of water. For example, the European Commission has set a target that the average domestic usage of water in the European Union should be reduced from 140 litres to 120 litres per person per day by 2020.

One of the biggest drains on our water supply in the developed world occurs when baths or showers are taken. Although it is widely acknowledged that a shower uses less water than a bath to clean oneself, this is only true when the shower is run for a short period of time or when the shower head is unable to deliver large volumes or high flow rates of water. Such high flow rate showers are typically referred to as ‘power showers’. Although providing a pleasurable and relaxing experience for many people, as well as affording the opportunity to wash away dirt and grime from our bodies, any type of shower (eco-shower, regular shower or power shower) that is allowed to run for a considerable period of time will produce large volumes of waste water. An average shower lasting no longer than five or six minutes will produce 50 litres of waste water. In reality, many showers last much longer or use higher flow rates so will waste larger quantities of water. Any efforts therefore to reduce water consumption from baths or showers, or to put the waste water to better use than to allow it to simply drain away, must be considered beneficial.

It would therefore be advantageous to have a system which is able to continuously re-circulate or recycle water from a shower system so that only a small quantity of water is used during the whole washing process. In addition, it would be desirable to change the source of the water flow within the circulating system so that fresh water can be introduced at a user's command, while at the same time evacuating the used waste water from the shower system. It would be especially desirable to be able to maintain the operating temperature and flow rate of the water within the shower system while it is being re-circulated, so that a user is not affected by irregularities in the temperature or pressure of the water with which they are washing.

SUMMARY OF THE INVENTION

The invention provides a water recirculation system comprising a plurality of reservoirs supplied from a water source; a washing unit to receive water from the reservoirs; a pump connected to return water from the washing unit to the reservoirs; and switching means for selecting from which of the reservoirs the washing unit receives water.

The water recirculation system is preferably configured so that users may make use of the washing unit to clean themselves with water that has been stored in one of the reservoirs. The reservoirs, which preferably contain heating elements, are supplied with water from a mains supply which optionally may pass through a non-return valve. The washing unit is preferably a shower unit and further comprises a waste trap incorporating a filter. The water recirculation system is preferably configured so that a user may utilise heated water that is circulated from one of the reservoirs in a continuous fashion in order to wash themselves, before switching to heated water that is circulated from a second reservoir. In this way, a limited quantity of water is circulated through the recirculation system allowing a user to save water during the process of taking a shower. The user may switch the source of the water, at their discretion, to permit a fresh supply of clean water to be introduced into the recirculation system from the second reservoir in order to rinse away, for example, excess cleaning products.

The waste water from the shower is collected and optionally passes through a flow switch before being returned to the active reservoir by the action of the pump. Preferably a multi-way junction is positioned downstream from the pump so that water may be routed to a selected one of the reservoirs at the command of the user. Each reservoir has separate inlet and outlet means to distribute water from a) the water source to the reservoirs, b) the pump to the reservoirs, c) the reservoirs to the washing unit and d) the reservoirs to a drain. The inlet and outlet means to distribute water around the recirculation system are preferably solenoid-operated valves to control the circulation of water, filling of the reservoirs and, as will be seen, the evacuation of waste water from the system. The control means are ultimately commanded by a user, according to their own specific needs.

It is preferable that at the same time as switching the source of the water circulating within the system from one reservoir to another, a simultaneous evacuation of the waste water occurs. When the water source is switched, the system purges the waste water from the reservoir no longer supplying the shower unit by displacing the waste water with clean water which is received preferably under pressure from a mains water supply. The waste water previously contained within the reservoir is discharged out of the recirculation system through a drainage port. The clean water entering the reservoir is then heated in readiness to be supplied to the shower unit as and when required. It is therefore preferable that a user is able to switch the water supply from a first reservoir to a second reservoir, and back to the first reservoir as often as they require. It is preferable that the system operates with only one heater in use at any one time in order to save energy usage.

It is preferable that the system further comprises a supplementary tank located between the washing unit and the pump, which provides a supply of water for the pump to draw from when first operated. The supplementary tank may also preferably comprise a sensor to determine the volume of water in the tank. When the volume of water falls below a pre-determined limit, the sensor will cause the supplementary tank to be re-filled with water. The system may further comprise a bypass pipe from one of the reservoirs to the supplementary tank, whereby water can be circulated through the system while bypassing the washing unit used. The system can be programmed to periodically circulate the water in this way prior to use of the washing unit so that the water within the system can be maintained to a sufficient temperature for washing. In this way, when a user commences a shower, there is no delay or lag in having to wait for water of a desirable temperature to warm up in the system. It is available on demand.

It is also highly preferable that the water recirculation system has a self-cleaning function, allowing the system to raise the temperature of the water in the reservoirs to a sufficiently high temperature in order to kill water borne pathogens. It is envisaged that a safety means will be introduced that does not permit users to implement the self-cleaning step of the system while they are using the shower, in order to avoid the risk of scalding themselves with hot water.

It would be highly preferable if the system comprises a cleaning apparatus for killing water borne pathogens, preferably in at least one or in both of the reservoir tanks A silver electrode based cleaning apparatus has been proven to be highly effective at minimising or reducing water borne pathogens in a supply of water. When programmed to do so, a small quantity of silver ions is introduced into one or more of the reservoir tanks by application of a small current across the silver or silver-copper electrode.

The invention as described above solves the problem of providing a water recirculation system that may be used to continuously re-circulate or recycle a small quantity of water while a user takes a shower. In particular the water recirculation system permits the user to change the source of water that is flowing within the recirculation system so that a fresh supply of water may be introduced into the shower at a user's command. The system also permits the simultaneous evacuation from the shower system of waste water that has been generated. In addition, the water recirculation system does not limit a user's experience of taking a shower as the user is not affected by irregularities in the temperature or pressure of the flow of water when the water recirculation system is operating because the circulating water is isolated from the remainder of the household water system. Because of the small total amount of water in the system, the heaters are able to maintain a constant temperature of the water even when the waste water evacuation and replacement steps are performed. Most particularly the water recirculation system is capable of operating while recirculating only about 5 litres of water, allowing significant savings to water consumption and cost to be made. With a sufficiently powerful pump, flow rates well in excess of 10 litres per minute can be achieved, to compare favourably with the experience of existing ‘power showers’ but without that flow of water running to waste.

DRAWINGS

FIG. 1 shows a schematic representation of the water recirculation system according to a first embodiment of the present invention;

FIG. 2 shows a schematic representation of the water recirculation system according to a second embodiment of the invention, while operating in a preheat mode;

FIG. 3 shows a schematic representation of the embodiment of FIG. 2, while operating in a mode that permits normal use of the washing unit;

FIG. 4 shows a schematic representation of the embodiment of FIG. 2, while operating in a mode that flushes used water from the first reservoir tank;

FIG. 5 shows a schematic representation of the embodiment of FIG. 2, while operating in a mode that flushes used water from the second reservoir tank; and

FIG. 6 shows a schematic representation of the water recirculation system according to a third embodiment of the invention, while operating in a mode that flushes used water from the washing unit.

Referring now to the drawings, FIG. 1 shows a schematic representation of the water recirculation system according to the present invention, as described in more detail below.

The system 1 comprises a shower unit 2 in connection with a pump 4 and two water reservoir tanks 6 a,6 b, which may conveniently be located beneath a shower tray (not shown) in the base of the shower unit 2. The shower unit 2 may be any standard shower unit with a shower head 8 as is familiar to a person skilled in the art. The tray of the shower unit 2 contains a waste trap 10 to collect the water from the shower head 8, which either falls directly into the waste trap 10 from the shower head 8 above or is water spray that runs from the sides of the shower unit 2 or from a user of the shower and accumulates in the waste trap 10. The waste trap 10 also incorporates a fine, e.g. 250 μm, filter (not shown) to prevent waste elements from the used shower water, such as body hair or grains of dirt, from entering the recirculation system, where they could prevent the correct operation of the valves for example.

The pump 4 is connected to the waste trap, from which it pumps water, preferably via a flow switch 12. The pump 4 will typically have a power in the range 300 W to 600 W, depending on the flow rate that is desired and the resistance to flow that is presented by the recirculation system 1. The outlet of the pump 4 is connected to the inlet of a first three-way junction 14, which in turn has two outlets coupled respectively to the two reservoirs 6. The flow switch 12 prevents the pump from operating if there is an insufficient flow of water from the waste trap, which could cause the pump to run dry and be damaged. Insufficient flow is most likely to be the result of a blocked filter and the user may be given a message via the control panel to indicate that the filter should be cleaned.

The reservoir tanks 6 may be made from any suitable material such as steel, copper or plastic that will not degrade in the presence of hot water. Each of the tanks is configured to hold a quantity of water that will be re-circulated through the system when a user takes a shower. It is anticipated that each of the tanks will typically have a capacity of about 3 litres of water, in order for the water recirculation system to remain economical in terms of water and power usage, although it is anticipated that the reservoir tanks may hold any sufficient quantity of water to permit a user to take a shower, bearing in mind that some water will inevitably be lost from the system during use owing to wetting of the user and of the walls of the shower unit 2. The relatively small capacity of the reservoir tanks 6, in comparison with the amount of water that is typically used during a normal shower, will not affect the performance of the recirculation system 1. It is envisaged that the recirculation system 1 will be able to consistently deliver flow rates of between 11 and 22 litres of water per minute in use, which compares favourably with flow rates of normal showers which are only in the region of 6-9 litres per minute. Although illustrated as discrete components in the schematic FIG. 1, the reservoir tanks 6 a,6 b may conveniently be located adjacent to one another, or may even be two sub-divisions of a single tank, which among other benefits reduces the surface area through which heat may be lost to the surroundings.

Each tank 6 also comprises a heating element 16 of a power sufficient to raise the temperature of the water in the tank rapidly to a desired temperature for taking a shower, for example 40° C. For example, a 3 kW heater may raise 3 litres of water to 40° C. in approximately 70 seconds. Once up to temperature, the rapid recirculation of a small quantity of water through the system results in a short time to return to the heater and only low power is then required to maintain the water at the desired temperature. The temperature may be selected by the user and maintained by switching the heater 16 on and off under the control of a thermostat in a conventional manner.

Each tank 6 is fitted with a pair of inlet valves 20,22 and a pair of outlet valves 24,26 in order to regulate the flow of water between the tank 6 and the other parts of the system 1. The inlet and outlet valves 20,22,24,26 are individually controlled by solenoids under the command of an electronic controller (not shown), and connect the various components of the recirculation system 1 as follows.

The tanks 6 are filled with water which is supplied from a mains water supply 18 through a non-return valve 28 to prevent back-flow of water from the system 1 into the mains. Water from the mains supply 18 enters a second three-way junction 30, which distributes it to the respective tanks 6 a,6 b. A first inlet valve 20 on each tank can be operated to permit or prevent the flow of water from the mains water supply 18 into the tank 6. A second inlet valve 22 on each tank 6 can be operated to permit or prevent the flow of water from the pump 4 to the tank 6. A first outlet valve 24 on each tank 6 can be operated to permit or prevent the flow of water from the tank to the washing unit 2 through a third three-way junction 32 that connects both tanks 6 a,6 b to the washing unit 2. A second outlet valve 26 on each tank 6 can be operated to permit or prevent the flow of water from the tank to a drain 34.

In use, water is supplied from the mains water supply 18 to the system 1 prior to a shower being taken for the first time in order to fill up at least a first one of the tanks 6 a through its open first inlet valve 20. The first inlet valve 20 is then closed and the heater 16 heats the water in the first tank 6 a to the required temperature as defined by a user on a control panel (not shown) and the user may commence their shower. The first outlet valve 24 and the second inlet valve 22 are then opened to create a circuit through the tank 6 a, the shower unit 2 and the pump 4. The pump is operated to push water from the tank 6 a to the shower head 8 and is available for the user to wash themselves. Water and associated residue from the showering process collects in the waste trap 10 which filters out any significant foreign objects from the system. It is anticipated that the waste trap 10 will be designed to allow the filter to be removed easily so that it may be cleaned and maintained on a regular basis. As previously described, the water is removed from the waste trap 10 by the action of the pump 4, which returns the water to the first tank 6 a after passing through the flow switch 12.

The water that is returned to the first tank 6 a is therefore continuously circulated within the system 1, being re-heated to raise it to the desired temperature each time it passes through the tank 6 a. When a user decides that the recirculating water is no longer sufficiently clean for washing, e.g. because it has become contaminated with dirt or with soap, shampoo or any other cleaning product, the user will require a fresh quantity of water with which to rinse themselves.

While water from the first tank 6 a has been circulating through the system 1, the second tank 6 b has been filled from the mains supply 18 and has also been heated to the user's desired temperature. Preferably, in order reduce the maximum power consumption, only one of the heaters 16 is operated at any time, with the heater 16 in the active tank 6 taking priority. Nevertheless, after the water in the first tank 6 a has reached its desired temperature the associated heater should need to be operated only intermittently in order to maintain that temperature, thereby allowing sufficient time for the heater in the second tank 6 b to raise the temperature of the second volume of water to the same level.

The user switches the flow of water circulating within the system 1 from the first tank 6 a to the water from the second tank 6 b by selecting the appropriate function on the control panel (not shown). The second inlet valve 22 and the first outlet valve 24 of the first tank 6 a are closed and the corresponding valves of the second tank 6 b are opened to create a new circuit through the second tank 6 b, the shower unit 2 and the pump 4. The pump is operated so that the clean water from the second tank 6 b is introduced into the system and circulates in a manner analogous to that already described.

Simultaneously, or after a short delay, the second outlet valve 26 of the first tank 6 a—which has remained closed throughout the procedure described up to now—is opened to allow the dirty water that was flowing within the recirculation system 1 via the first tank 6 a to be sent to the drain 34 and evacuated from the system 1. The first tank 6 a is then re-filled with fresh water from the mains supply 18 and it is heated to the same temperature as previously selected in readiness for the next changeover of water supply if the user requires it. Preferably, the flow of water under mains pressure into the first inlet 20 of the tank 6 is used to displace the dirty water from the tank 6.

A user may switch the flow of the water within the water recirculation system 1 as often as they require within the course of a single shower, although it is expected that in most cases the user will use the water supply from each tank 6 only once. In this way, significant savings can be made in terms of water usage, which are mirrored by associated savings in energy consumption of the water recirculation system.

The water recirculation system 1 has a self-cleaning function, in which, when the shower is not in use, the heaters 16 can be used to raise the temperature of the water in the reservoirs 6 to a temperature high enough to kill water-borne pathogens, for example 65° C. This function could be instigated by the user from the control panel or automatically at predetermined time intervals. A safety means will be provided that prevents the pumping of high temperature water from the reservoirs 6 to the shower unit 2 while the self-cleaning operation is progress, in order to avoid the risk of scalding.

The system as described and illustrated has two reservoirs 6 a,6 b and the user may switch the water supply alternately between them. It will readily be understood that a larger number of reservoirs 6 could be provided, with the respective inlet and outlet valves 22,24 being operated so as to cycle the water supply among each of them in turn.

The reservoirs need not be simple tanks but can be any suitable shape that enables a sufficient volume of water to be held in thermal communication with the heater element. In particular, each reservoir 6 may contain internal walls (not shown) that define a one-way path from the inlet valves 20,22 to the outlet valves 24,26. This arrangement would help to ensure that, when clean water from the mains supply 18 is used to displace dirty water from the tank 6 to the drain 34, there is minimal mixing between the clean and dirty water. On the other hand, it would reduce convection within the tank that might otherwise help to ensure a uniform water temperature. Taking this development a stage further, each reservoir could take the form of a coiled or convoluted pipe with the heater element running along its length.

Forms of heating other than electrical elements could be used in connection with the invention. For example, with a more complex plumbing arrangement, the water could be directed to pass through the heating unit of a combination boiler. It might be possible for all of the reservoirs to share a common heating unit.

As described, each of the inlets and outlets 20,22,24,26 of the tank 6 is regulated to be opened or closed by its own solenoid-controlled valve. By changing the configuration of open and closed valves, different circuits and flow paths through the system 1 can be selected. A different way of achieving the same end would be to remove the inlet and outlet valves 20,22,24,26 from the tanks 6 and to insert multi-way valves in place of the three-way junctions 14,30,32. The flow paths through the system 1 could then be reconfigured by changing the positions of the multi-way valves. For example the first three-way junction 14 could be replaced by a valve with three positions: one that blocks the flow of water from the mains supply 18, one that directs water from the mains supply 18 to the first tank 6 a, and one that directs water from the mains supply 18 to the second tank 6 b.

FIGS. 2-5 show various modes of operation of a second embodiment of the invention as will now be discussed in more detail. This embodiment functions in a manner analogous to that already described for FIG. 1, with additional features discussed in more detail below. The direction of water flowing in the water recirculation system 1 is shown on each of FIGS. 2-5 by a series of arrows. The flow of water is directed by selectively opening and closing valves, which are shown in the Figures as filled circles when closed and as empty circles when open. The valves are preferably solenoid controlled. Further non-return valves (not shown) may be placed in series with some or all of the solenoid-controlled valves where necessary to prevent leakage of water due to reverse pressure differences that can arise.

FIG. 2 shows that, compared with the system of FIG. 1, the water recirculation system 1 further comprises a supplementary tank 36 which is connected to the waste trap 10 of the washing unit 2. Water from the waste trap 10 enters the supplementary tank 36 and exits from the underside of the supplementary tank 36 prior to being circulated around the system 1 by the pump 4. The supplementary tank 36 contains enough water so that it is able to supply and fill all of the pipes in the water recirculation system 1 so that when the pump 4 is first operated it does not run dry before the water has completed its circuit, i.e. before water that has been pumped to the washing unit 2 begins to return from the waste trap 10 to the inlet of the pump 4. The supplementary tank 36 is filled with water from the mains supply 18 prior to use of the washing unit 2.

The system of this embodiment further comprises a bypass pipe 37 that is not present in the system of FIG. 1. The bypass pipe 37 permits water to circulate from the first reservoir 6 a to the supplementary tank 36 without passing through the washing unit 2, when valve 44 is closed and valve 42 is open. When the preheat function of the water recirculation system 1 is started, valve 22 b and 44 are closed and valves 22 a and 42 are opened. Water from the supplementary tank 36 is supplied to the pump 4 and transmitted to the reservoir 6 a after passing through the first three-way junction 14. Water exits the reservoir tank 6 a through pipe 38 and passes through a fourth three-way junction 40, before passing through valve 42 and along the bypass pipe 37 to return to the supplementary tank 36. A non-return valve 46 between the waste trap 10 of the washing unit 2 and the supplementary tank 36 prevents the pressurized water flowing up from the supplementary tank 36 into the waste trap 10 of the washing unit 2.

The heater (not shown in FIG. 2) in the reservoir 6 a is operated during this cycle so that a flow of preheated water is circulated within the interconnecting pipes of the system so that water of a preset temperature may be transmitted to the washing unit 2 at the exact time that a user commences taking a shower. It is likely that if the supplementary tank 36 and the pipework are sufficiently well insulated, the pump 4 will need to be operated only intermittently to maintain the water in the system at an acceptable temperature.

FIG. 3 shows the typical flow of water in the water recirculation system 1 of FIG. 2 when the washing unit 2 has been turned on and water is circulating through the system 1. This mode of operation of the system is essentially the same as previously described in relation to the embodiment of FIG. 1. The flow of water through the system 1 is the same as just described for FIG. 2 up until the point where the water enters the fourth three-way junction 40. Instead of exiting the fourth three-way junction 40 through valve 42, the flow of water is directed through valve 44 and enters the third three-way junction 32, from where it is transmitted to the washing unit 2 (valve 24 b being closed to prevent the water entering the second reservoir 6 b). Water exiting the washing unit 2 through the waste trap 10 then drains into the supplementary tank 36.

As previously described in connection with the embodiment of FIG. 1, when the user decides that the recirculating water has become too dirty or soapy, the user can opt to switch the source of water for the washing unit 2 from the first reservoir 6 a to the second reservoir 6 b, e.g. by pressing a button. Valve 22 a is then closed and valve 22 b is opened so that water pumped into the first three-way junction 14 is diverted into the second reservoir 6 b. Hot water is thus displaced from the second reservoir 6 b via the pipe 47 and the third three-way junction 32 to the washing unit 2. Meanwhile, by opening valve 20 a and keeping valve 20 b closed, fresh water from the mains supply 18 can be introduced into the first reservoir 6 a via the second three-way junction 30 to displace the dirty water from reservoir 6 a through valve 26 a to the drain 34. Then, while water from the second reservoir 6 b is being used to supply the washing unit 2, the fresh water in the first reservoir 6 a can be heated ready for use when the user decides to switch reservoirs 6 a,6 b again.

Because some used water remains in the pipework and in the supplementary tank 36 at all times, switching the source of water for the washing unit 2 from one reservoir 6 a,6 b to the other reservoir 6 b,6 a will not immediately replace all of the used water in the system 1 with fresh water. The proportion of water replaced on each changeover will depend on the capacity of the reservoirs 6 a,6 b relative to the remainder of the system 1. For the maximum use of fresh water, it is possible to program a “rinse” mode of operating the system 1 that automatically and repeatedly switches between the reservoirs 6 a,6 b as soon as the next reservoir 6 a,6 b has been filled and raised to the desired temperature. Of course, operating in this mode will detract from the water- and energy-saving benefits that the system 1 is capable of providing.

After usage of the system 1 has occurred, the various pipes and in particular the supplementary tank 36 and at least one of the reservoirs 6 a,6 b will be filled with used water. It may be desirable to flush the system with fresh water, e.g. before the washing unit 2 is used by a different person. FIG. 4 shows a mode of operation of the embodiment of FIG. 2 wherein water from the first reservoir tank 6 a is expelled from the system 1 using mains water pressure. This mode of operation makes use of a flushing pipe 49 between the mains water supply 18 and the supplementary tank 36 that has no equivalent in the embodiment of FIG. 1.

Fresh water enters the system 1 from the mains water supply 18 and, by closing valves 20 a, 20 b and opening valve 48, is routed through the second three-way junction 30 and a sixth three-way junction 51 before passing into the supplementary tank 36. The fresh water dilutes and displaces the used water from the supplementary tank 36, which passes through the non-operating pump 4 before being transferred to the first three-way junction 14. Valve 22 a is open and valve 22 b is closed so the flow of water is directed into the first reservoir tank 6 a, and exits from the first reservoir tank 6 a through valve 26 a before passing through the fifth three-way junction 50 and exiting the system 1 at the drain 34.

FIG. 5 shows another mode of operation of the embodiment of FIG. 2, wherein water from the second reservoir tank 6 b is expelled from the system 1. Water enters the system 1 from the mains water supply 18 and, by closing valves 20 a and 48 and opening valve 20 b is routed through the second three-way junction 30 to enter the second reservoir 6 b. Valves 24 b and 26 a are closed so that the water exits from the second reservoir 6 b through valve 26 b and is routed through the fifth three-way junction 50 before being transmitted out of the system 1 through the drain 34. The system 1 will typically be operated in the mode shown in FIG. 5 as a second stage of flushing the system 1, sequentially before or after the mode shown in FIG. 4. However, if during the previous use of the washing unit 2 it was the first reservoir 6 a that was active, then as described above in connection with FIG. 3 the second reservoir 6 b will already have been flushed and refilled with clean water ready for a further request by the user to switch the water supply. Such a refilling operation uses exactly the same flow pattern as shown in FIG. 5. In those circumstances a further flushing of the second reservoir 6 b may be deemed unnecessary.

In a further mode of operation (not illustrated) for flushing the system of FIGS. 2 to 5, it is possible to set the various valves so that fresh water from the mains supply is directed to flow sequentially through the first reservoir 6 a, the supplementary tank 36 and the second reservoir 6 b to the drain, without passing through the flushing pipe 49. It will be understood that if this mode of flushing is to be adopted, the flushing pipe 49, the sixth three-way junction 51 and the valve 48 could therefore be omitted from the system.

FIG. 6 shows a third embodiment of a water circulation system 1 in accordance with the invention. It is identical to the system 1 in FIGS. 2 to 5, except that the pipe 38 from the first reservoir 6 a to the fourth three-way junction 40 and the pipe from the second three-way junction 30 to the second reservoir 6 b, instead of crossing over one another, intersect in a four-way junction 52. Water can thus flow into the four-way junction 52 either from the first reservoir 6 a or from the mains supply 18 via the second three-way junction 30. By opening or closing valves 20 b, 42 and 44, the water can be directed to flow out of the four-way junction 52 either to the second reservoir 6 b or to the fourth three-way junction 40. This gives additional flexibility over how the water flow through the system can be configured. For example, fresh water can be controlled to flow directly from the mains supply 18 through the four-way junction 52 and the fourth and third three-way junctions 40,32 to the washing unit 2, in order to flush used water from the standing pipe of the washing unit 2.

Despite the fact that FIG. 6 shows the use of a four-way junction 52 to provide an alternative route to flush used water from the system 1, it will equally be appreciated that, with appropriate settings of the various valves on the outlets from the four-way junction 52, the presence of the four-way junction 52 allows water to be directed around the system 1 in the manner as previously described for any of FIGS. 2-5.

For example, FIG. 6 shows the third embodiment of the invention configured to operate in the same manner as the second embodiment in FIG. 4. Fresh water enters the system 1 from the mains water supply 18 and, by closing valves 20 a, 20 b and opening valve 48, is routed through the second three-way junction 30 and a sixth three-way junction 51 before passing into the supplementary tank 36. The fresh water dilutes and displaces the used water from the supplementary tank 36, which passes through the non-operating pump 4 before being transferred to the first three-way junction 14. Valve 22 a is open and valve 22 b is closed so the flow of water is directed into the first reservoir tank 6 a, and exits from the first reservoir tank 6 a through valve 26 a before passing through the fifth three-way junction 50 and exiting the system 1 at the drain 34.

Even without the four-way junction 52 shown in FIG. 6, i.e. using the system shown in FIGS. 2 to 5, it is possible to configure the various valves such that fresh water from the mains supply 18 can be used to flush used water in the shower unit 2. The fresh water is directed under mains pressure into the one of the reservoirs 6 a,6 b that already contains clean water, which is in turn connected so as to supply the washing unit 2. Meanwhile water collected in the waste trap 10 can then be drained via the supplementary tank 36 into the other of the reservoirs 6 b,6 a and the pump 2 can be used to discharge that reservoir 6 b,6 a to the drain 34. 

1. A water recirculation system comprising a plurality of reservoirs supplied from a water source; a washing unit to receive water from the reservoirs; a pump connected to return water from the washing unit to the reservoirs; and switching means for selecting from which of the reservoirs the washing unit receives water.
 2. A water recirculation system according to claim 1, further comprising a non-return valve between the water source and the reservoirs.
 3. A water recirculation system according to claim 1, wherein at least one reservoir comprises a heater.
 4. A water recirculation system according to claim 1, wherein the washing unit is a shower.
 5. A water recirculation system according to claim 1, wherein the washing unit further comprises a waste trap incorporating a filter, to which the pump is connected.
 6. A water recirculation system according to claim 1, further comprising a multi-way junction connected to an outlet of the pump to distribute water from the pump to the respective reservoirs.
 7. A water recirculation system according to claim 1, wherein each reservoir has an inlet valve to control the flow of water from the water source to the reservoir.
 8. A water recirculation system according to claim 1, wherein each reservoir has an inlet valve to control the flow of water from the pump to the reservoir.
 9. A water recirculation system according to claim 1, wherein each reservoir has an outlet valve to control the flow of water from the reservoir to the washing unit.
 10. A water recirculation system according to claim 1, wherein each reservoir has an outlet valve to control the flow of water from the reservoir to a drain.
 11. A water recirculation system according to claim 7, wherein the inlet valves are controlled by solenoids.
 12. A water recirculation system according to claim 9, wherein the outlet valves are controlled by solenoids.
 13. A water recirculation system according to claim 1, wherein the switching means for selecting from which of the reservoirs the washing unit receives water is controlled by a user.
 14. A water recirculation system according to claim 5, further comprising a flow switch through which the water exiting the waste trap passes before entering the pump.
 15. A water recirculation system according to claim 1, further comprising a supplementary tank located between the washing unit and the pump.
 16. A water recirculation system according to claim 15, further comprising a non-return valve between the washing unit and the supplementary tank.
 17. A water recirculation system according to claim 15, further comprising means to distribute water from the water source to the supplementary tank.
 18. A water recirculation system according to any of claim 15, further comprising means to distribute water from the first reservoir to the supplementary tank.
 19. A method of re-circulating water in a system according to claim 1, the method comprising the steps of: supplying the plurality of reservoirs with water from a water source; heating the water in a first reservoir; supplying the washing unit with heated water from the first reservoir; and operating the pump to return the water from the washing unit to the first reservoir.
 20. A method of re-circulating water according to claim 19, wherein the step of operating the pump further comprises: collecting water from the washing unit in a supplementary tank; and supplying water from the supplementary tank to the pump.
 21. A method of re-circulating water according to claim 20, the method further comprising the step of: operating the pump to circulate the heated water from the first reservoir to the supplementary tank before the step of supplying the washing unit.
 22. A method of re-circulating water according to claim 19, the method further comprising the step of: flushing the system with water from the water source.
 23. A method of re-circulating water according to claim 19, wherein the recirculation of water is a continuous process.
 24. A method of re-circulating water according to claim 19, further comprising the step of switching the water supply to the washing unit from the first reservoir to a second reservoir.
 25. A method of re-circulating water according to claim 24, further comprising the step of, prior to switching the water supply from the first reservoir to the second reservoir, heating the water in the second reservoir to the same temperature as that of the water supply in the first reservoir.
 26. A method of re-circulating water according to claim 24, further comprising the step of, after switching the water supply from the first reservoir to the second reservoir, releasing the water in the first reservoir into a drain.
 27. A method of re-circulating water according to claim 26, further comprising re-filling the empty reservoir from the water source.
 28. A method of re-circulating water according to claim 27, wherein the step of re-filling comprises displacing the water in the reservoir to be emptied with pressurised water from the source.
 29. A method of re-circulating water according to claim 24, further comprising the step of switching the water supply to the washing unit from the second reservoir back to the first reservoir.
 30. A method of re-circulating water according to claim 19, wherein heat is applied to only one reservoir at a time.
 31. A method of re-circulating water according to claim 19, further comprising a self-cleaning step in which water in the reservoirs is heated to a high temperature.
 32. A method of re-circulating water according to claim 31, where the high temperature is sufficient to kill water borne pathogens.
 33. A water recirculation system according to claim 8, wherein the inlet valves are controlled by solenoids.
 34. A water recirculation system according to claim 10, wherein the outlet valves are controlled by solenoids. 